Electromagnetic circuit controller



MarchZO, 1945. 1.. BEEMAN ELECTROMAGNETIC CIRCUIT CONTROLLER Filed July5, 1939 7 Sheets-Sheet l ATTORNEY March 20, 1945. EE AN 2,371,501

ELECTROMAGNETIC CIRCUIT CONTROLLER Filed July 5, 1939 7 Sheets-Sheet 2IN V EN TOR. 25 fizz/mm A TTORNEY March 20, 1945.

L. BEEMAN ELECTROMAGNETIC CIRCUIT CONTROLLER 7 Shets-Sheet 3 Filed July5, 1939 uvmvrozev A2; 556444 A TTORNEY March 20, 1945. L. BEEMANELECTROMAGNETIC CIRCUIT CONTROLLER Filed July 5, 1939 7 Sheets-Sheet 4\l\\\ I f INVENTOR. [Ylf Eff/mm BY MA 44 ATTORNEY March 20, 1945. BEEMANELECTROMAGNETIC CIRCUIT CONTROLLER Filed July 5, 1939 7 Sheets-Sheet 6INVEN TOR. 1 v1: 550mm L ATTORNEY March 20, 1945. BEEMAN IELECTROMAGNETIC CIRCUIT CONTROLLER Filed July 5, 1939 7 Sheets-Sheet 7 95 0 H R 2 z 0 3 0 y 1 1 1 J V ,9 m M i a: w i W H u g 5 L 5 5 2 unnu. aJ AW \\q\\\\\\\\\\ I H M 1 u J W (aw A TTORNEY Patented Mar. 20, 19452,371,601 ELECTROMAGNETIC CIRCUIT CONTROLLER Lyle Beeman, Milwaukee,Wis, assignor to The' Master Electric Company, Dayton, Ohio, acorporation of Ohio Application July 5, 1939, Serial No. 282,857

24 Claims. (01. 175-294) This invention relates to electromagneticcircuit controllers for motors and other electrical equipment and hasfor a general aim to simplify and otherwise improve the construction andoperation of control devices of that type.

An object of the present invention is to provide in an electromagneticcircuit controller a novel combination and arrangement of parts by whichclosing and opening of the circuit may be effected by manipulation of asingle control eleresponsive devices operable upon a single switch tobreak the circuit in the event of an overload on' either of a pluralityof sides of the circuit.

Another object is to provide, in a circuit controller of the charactermentioned, a single pilot switch manually operable to effect closing andopening of the circuit and also automatically operable to open thecircuit in response to an overload thereon.

Another object is to provide a new and improved structural relationbetween the main switch and the electromagnetic actuator therefor.

Another object is to improve the construction and operation of theelectromagnetic actuator in a; controller of the character mentioned.

Another object is to provide an improved controller of the charactermentioned which shall be Fig. 4 is a sectional view taken along thesectlon line 4-4 of Fig. 3.

Fig. 5 is a fragmentary view illustrating the switch bar mounting means,

Fig. 6 is a front elevation of the pilot switch and its controlmechanism.

Figs. '7 and 8 are circuit diagrams.

Fig. 9 is a vertical sectional view of an electromagnetic switchembodying the present invention but of somewhat different form.

Fig. 10 is a front elevation partly in section of the motor controlswitch of Fig. 9, with the pilot switch and its control mechanismremoved.

Fig. 11 is a horizontal sectional view taken along the section line l|llof Fig. 9.

Fig. 12 is a vertical sectional view taken along theline.l2-|2ofFig.9.

Fig. 13 is a vertical sectional view taken along the line I3--l3 of Fig.10.

The electromagnetic switch shown in Figs. 1 to 6 is enclosed in anappropriate housing 10 having a removable front cover H equipped with anappropriate cupped opening l2 fashioned to accommodate a singlepush-button control element I3 more compact and capable of moreeconomical productionv without impairing reliability of operation orfacility of installation and inspection.

Other more specific objects and advantages will appear, expressed orimplied, from the following description of two illustrative embodimentsof the present invention.

Inv the accompanying drawings:

Figure 1 is a vertical sectional view of an electromagnetic switchconstructed in accordance with the present invention, and illustratingthe position of parts when the main switch is open.

Fig. 2 is a similar view illustrating the position of the parts when themain switch is closed.

Fig. 3 is a front elevation partly in section with the pilot switch andfits control mechanism removed.

hereinafter further described.

All of the parts are supported by a mounting plate [4 removably fixed tothe rear vertical wall of the housing by suitable means, such as a pairof hookedlugs I5 struck up from the wall of the housing and embracingthe lower edge of the plate I4 and a removable screw l6 which passesthroughthe upper end of the plate l4 and into the rear housing wall. Thearrangement is such that, with the cover ll removed, all of the partsmay be removed, as a unit, from the housing, by removing the screw itand lifting the plate I 4 away from the lugs l5. 7 I

Projecting forwardly from the upper portion of the mounting plate I4 isan insulating structure providing a rigid support for pairs of contactmembers I1 and. I8 constituting parts of the main switch. This structurecomprises a pair of end plates 20, secured through appropriate brackets2| to the mounting plate l4, partition plates 22 parallel to the endplates 20, and interposed separator blocks 23, the'several plates andblocks being formed of suitable insulatingmaterial and threadedengagement with the metal bracket 28 carrying a binding post 29; and theother contact l8 of each pair constitutes the head of a stud 30 imbeddedin the same block 23 and in threaded engagement with a metal bracket 3|carrying a binding post 32. The main switch includes pairs of contacts33 and 34 simultaneously movable into and out of contact with the pairsof fixed contacts I! and 3, respectively. ,Each pair of moveablecontacts 33 and 34 are electrically connected and supported by ametallicbridge piece 35 having at its mid point oppositely projectingears 36 which extend into guide slots 3? formed in the parallel legs 38of a U-shaped carrier bracket 39. Each bracket 39 is securely fixed atits base in a movable switch bar 45, the legs 3B of Y the'bracketextending upwardly and closely embracing the bridge piece 35 in a mannerto further guide the latter. and thereby maintain the moveable contacts33 and 34 properly aligned with their mating fixed contacts I! and I8,respectively. Each bridge piece 35, and the contacts 33 and 34 carriedthereby, are yieldably supported and urged upwardly by a compressionspring 4! disposed within the bracket 39,'the ears 36 cooperating withthe upper ends of the slots 31 to limit upward movement of the contactsrelative to their carrier bracket 39.

The movable switch bar 40 is formed of suitable insulating material. -Itis supported and guided at its ends by parallel metallic strips .42

which extend downwardly from the end' plates 26 of the switch'supportingstructure through appropriate guide grooves 43 formed in the oppositeends of the bar 4!]. Each strip 42 is adjustably but securely anchoredat its upper end in a groove 44 formed in the outer face of itssupporting plate 25 (Fig. a screw 45, extending through a slot 45' inthe strip and threaded into the plate 29, serving to releasably fix thestrip in the position shown. Upon loosening the screws 45 the strips 32may be retracted lengthwise of their respective mounting grooves 43 in amanate the latter. These links 58, secured byscrews 59 to the switch bar40, extend downwardly therefrom in the direct line of motion of the bar,as determined by the guide strips 42, and are connected at their lowerends tothe armature by a pin 60, which extends transversely through thearmature and into engagement with the links.

The arrangement is such that, while the electromagnet is de-energized',the armature assumes the lower position shown in Fig. 1, in whichposition the switch bar 40 is lowered and the pairs of movable contacts33and 34 carried thereby are withdrawn from the pair of fixed contactsIT and I8. In this position the armature is supported by the engagementof the leg 52 thereof against the stop pin 55 and by the engagement ofthe fulcrum pin 53 against theupper ends of the slots 54': When the coil46 of the electromagnet is v energized, however, the armature movesupwardly into the position shown in Fig. 2 with the legs thereof incontact with the legs of-the field piece, and by this movement theswitch bar 40 is elevated by the direct thrust of the links 58 and thepairs of contacts 33 and 34 are thereby elevated net to efiectwithdrawal thereof from the ends of the switch bar 35, to thus permitready removal of the bar. Due to this arrangement, ready access may behad to both the fixed and movable contact members of the switch for thepurpose of cleaning or replacing the same.

The switch bar 33 is actuated by an appropriate electromagnet preferablydisposed below the main switch supporting structure. In this instancethe electromagnet shown comprises a conventional winding or coil 35supported by a core ll comprising one leg of an L-shaped laminated fieldpiece whose other leg 58 is securely fixed by bolts 49 to and betweenparallel struck-up portions 55 of the mounting plate it. Theelectromagnet shown also includes an L-shaped laminated armature havingone leg 5! disposed to cooperate with the projecting end of the core 41and another leg 52 disposed to cooperate with the ad-* jacent end ofthe, leg 58 of the field piece. A pin" 53, projecting laterally throughthe end of leg 52 and loosely engaged at its opposite ends in verintopressure contact with the mating pairs of fixed contacts I? and I8;

The stop pin 56 is mounted in a novel manner to render the same readilyremovable. It rests at its opposite ends in suitable perforations in thespaced parallel side members of the bracket 51 and is retained 'in placeby a resilient steel clip 60 which spans the bracket 5! and which isprovided with ends '6! bent in a manner to resiliently press against theopposite sides of the bracket and thereby frictionally retain the clipin'place. The ends 5| of the ,clip normally overlie the ends of the pin56 to retain the same against longitudinal' displacement, the cliphowever being readily removable to permit lengthwise with-. drawal ofthe pin 56.

1 It will be noted that the slots 54 are open attheir lower ends, sothat, upon removal of the stop pin 56, the armature of the electromagnetmay be readily removed. Also, since retraction of the guide strips 32permits withdrawal of the switch bar 40 and the contacts carriedthereby, these parts together with the links 53 and armature constitutea sub-assembly which may be readily removed, as a unit, from the rest ofthe mechanism. I

As indicated in the diagram of Fig. 7, the coil 46 of the electromagnetis included in a shunt circuit 52 connected across two of thosestationary switch contacts ll which, in use, are directly connected withthe power line. Included in this shunt circuit 62 is amanuallycontrolled pilot switch 63, which is about to be described, anda normally closed thermal overload switch 55, which is controlled by twoheater coils 55 connected in two sidestfi of the motor circuit in amanner to be hereinafter described. The pilot switch shown in Figs. 1,2, and 6 is of novel construction. It'is enclosed in a hous on the freeend of a rocker plate I3, which is fulcrumed at its other end M againstan upstanding portion 15 of a bracket plate 15 fixed to the bottom ofthe housing. The center of the rocker plate 18 is cut away toaccommodate a tension spring 11, which extends from the switch carryingend of the rocker plate 13 beyond the fulcrumed end 14 thereof to thebent end 18 of a rocker control plate 19. This rocker control plate 19is cut away at its center to clear the switch carrying plate 13 and itssupports 15, and is fulcrumed, as at 80, against a pair of up-standingportions 8| of, a bracket plate 82 fixed to the base of the switchhousing.

It will be noted that with the parts of the switch in the position shownin Fig. l, the line of tension in the spring 11, corresponding to [theaxis of the spring, lies at one side of the fulcrum point 14 of theswitch carrier plate 13, so that the switch is retained by the spring inthe open position shown. And it will be understood that as the controlplate 19 is swung upon its carrier plate 13, thereby causing the switchto close with a snap'action. Likewise, as the con- 7 trol plate 19swings from the position of Fig. 2

toward the position of Fig. 1, the line of tension in the spring againshifts to the other side of the fulcrum 14, causing the switch to openwith a snap action.

It will also be noted that, regardless of the position of the controlplate 19, its fulcrum 80 always remains at one and the same side of theline of tension in the spring 11, so that the control plate is alwaysurged by the spring 11 toward the position shown in Fig. 1, and theswitch is thus normally biased toward the open position of Fig. 1. Apush pin 83, guided inthe base of the switch housing 61 and bearingagainst the control plate 19. is operable to force the plate 19 towardthe position of Fig. 2 to thereby close the switch in the manner abovedescribed, the position of the pin 83 being controlled in this instanceby a spring strip 84.

In this instance, the housing 51 of the pilot .switch is mounted uponone end of an appropriate bracket plate 85, the other end of which isreleasably interlocked with and supported by ,the bracket 51 hereinabovementioned. The bracket 51 comprises two parallel plates 51-proiectingfrom and fixed to the mounting plate I4 by screws 88 (Fig. 3) whichextend through bent portions 81 at their inner ends. The bracket plate85 extends between the plates 51 and is recessed at its opposite edges89 to receive and interlock with those plates, as indicated particularlyin Fig; 6, each plate 51 alsobeing notched at its opposite edges toreceive and interlock with the bracket plate in a manner to releasablybut rigidly support the latter. Thefplate 85 may be readily released andremoved from the structure 51 by spreading the plates 51 apart and outof the recesses 89 in the plate 85. The

plate 85 is cut away, as at 9|, to accommodate,

the switch control strip 84 heretofore mentioned. The control strip 84is securely attached at one end 82 to the pilot switch box 01, makescontact at its other end 93 with a shoulder 94 on a rocker element 95,and intermediate its ends makes contact with the switch operating pushpin 83 above mentioned.

The rocker element is supported by a pivot pin 95, fixed in a U-shapedstructure 88 fixed to the bracket plate 85 between plates 51, and isprovided with stop shoulders 91 and 98 which coact with the structure 88to limit the rocking action thereof, The spring strip 84 yieldably urgesthe rocker element 95 toward the position shown in Fig. 1 with theshoulder 91 thereof against the structure 88. The rocker element 95 isalso provided with a shoulder 99 for coaction with the end I00 of thespring strip ml which is attached at its other end I02 to the leg 52 ofthe armature of t the electromagnet, the arrangement being such that,when the armature has been advanced into the position shown in Fig. 2,the spring strip IOI yieldably retains the rocker element 95 in aposition with its stop shoulder 98 against the structure 88. It will benoted that in this position of the rocker element 95, the spring strip84 and push pin 83 are held thereby in such position as to hold thepilot switch 63 closed.

It will thus be noted that the rocker element 95 controls the pilotswitch S3 and is capable of assuming two positions, the one illustratedin Fig. l in which the pilot switch is open, and the other illustratedin Fig. 2 in which the pilot switch is closed.

Provision is made for shifting the rocker element from either-positionto the other, alternatively, by successive movements .of a single con-'ported upon a pin I06 fixed in the stem. The pointed end of the dog I05projects toward the rocker element 95 and the other end is fashioned toprovide a fiat face I01 which coacts with leaf spring I08 to yieldablyretain the pointed end disposed centrally of the stem I03. The rockerelement 95 is provided with a V-shaped cam I09 symmetrically disposedwith respect to its fulcrum pin 96 and. projecting toward the dog I05,

recesses I I0 and III being formed at the base of the cam I09 atopposite sides of the fulcrum pin 95.

The arrangement is such that with the rocker element 95 in the positionshown in Fig. 1, inward movement of the button I3, under pressure,causes the point of the dog I05 to advance along the under face of thecam I09 into and against the base of that recess IIO disposed below thepin 96, and continued advance of the dog thereafter forces the rockerelement 95 to rock counter-clockwise toward and into the position ofFig.2. However, whenever the rocker element 95 is in the position ofFig. 2, inward movement of the button I3, under pressure, causes thepoint of the dog to advance along the upper face of the cam I09 into andagainst the base of that recess III disposed above the pin 95, andcontinued advance of the dog thereafter forces the rocker element 95 to.rock clockwise toward and into the position of Fig. 1.

It will thus be understood that with the pilot switch 63 open, thearmature 5I of the electro push-button I3 to thereby close the pilotswitch 83 in the manner above described. Of course the circuit 82 (Fig.7) is closed by the closing of the In this instance the button I 3 pilotswitch 63 and the coil 45 of the electromagnet is thereby energized,causing the armature iii-52 to move into the Fig. 2 position and therebyactuating the switch bar 46 to close the main switch. As above noted,the rocker element 95 is yieldably retained in the switchclosing-position of Fig. 2 by the spring Ifll as long as the armatureI-52, to which it is attached, remains in the Fig. 2 position, so thatwhen the operating pressure is released from the push button I3, the

' switch 63 to open and thus break the circuit 62,

so that the electromagnet coil 46 becomes deenergized and its armature5I-52 falls, retracting the switch bar 40 and thereby opening the mainswitch. Again the rocker element 95 remains undisturbed by automaticretraction of the push button I3, and the several parts remain in thepositionsshown until the push button I3 is. again depressed.

Provision is also made for automatically opening the main switch in theevent of an overload in the motor circuit. In this instance a'secondswitch 66 and heating coils 65, previously referred to, are utilized forthis purpose.

The switch 64 is shown enclosed in a housing II3 of insulating materialattached to the mounting plate Itbetween the two end plates26 of themain switch supporting structure. As indicatecl in Fig. 2, it includestwo fixed contacts H4 and cooperating movable contacts H5, like theswitch 63 previously described, and is otherwise substantially the sameas the latter except that the spring I I6 and rocker control plate IIIare so arranged that the switch 65' is normally biased toward closedrather than toward open position. It will be noted that in switch 66 thespring H6 is disposed on the left side (Fig. 2) of the fulcrum point II8 of the control plate I II, in

which position the latter is always urged toward the left. It will alsobe noted that in the left extreme position of the control plate III thespring H6 is on the left side of the fulcrum point I IQ of the switchcarrier plate I26, thereby urging the latter toward switch closingposition; but when the control plate H1 is swung towardthe right thespring H6 shifts to the other side of the fulcrum point II9, therebyopening the switch with a snap action. f

In this instance the end of the control plate III of the switch 6extends through anopening I2I in the housing I I3 and projects into therange of movement of two levers I22. As indicated particularly in Fig.4, levers I22 extend horizontally in opposite directions from the plateI I1, each being rockably mounted intermediate its ends upon anappropriate bracket arm I23 fixed to a side of the switch housing I I3.The outer or remoteends I25 of the levers I22 overlie the free ends I25,respectively, of separate bi-metallic thermostatic strips I26 of a wellknown type.

In this instance the thermostatic strips I26 are disposed at oppositesides of the electromagnetic coil 46, each being securely fixed at itslower end I21 in a C-shaped bracket I28 and extending upwardly through ac-shaped bracket I29 to a point adjacent the end I24 of one of thelevers I22, as indicated in Fig. 1. A heating coil in the form of ametallic strip 65 is arranged close to and substantially parallel toeach of the thermostatic strips I26, so that the latter is influenced bytemperature variations in the strip 65. Each heating coil or strip 65 isconnected in aside of the work circuit 66, as indicated in Fig. '7, sothat the temperature of each corresponds to the load on that side of thework circuit and so that the temperature of the adjacent thermostaticstrip also corresponds thereto.

. Each'heating coil or strip 65 is shown with its ends attached to andsupported by the C-shaped brackets I28 and I29 which are in turn mountedupon an elongated block I30 of insulating material attached to themounting plate I4, the adjacent thermostatic strip I26 being suspendedbetween the heating strip 65 and block I36.

The arrangement is such that should either side of the work circuit 66becomes overloaded, causing an abnormal rise in temperature in eithercoil 65,- the adjacent thermostatic strip I25, reacting to thattemperature rise, will flex and operate its associated lever I22 in adirection to force the control plate II'I toward the right (Fig. 1)thereby causing the switch 64 to open and thus deenergize the coil 46 ofthe electromagnet. When this occurs, the armature 5l-52 of coursef-alls, retracting the switch bar 40 and opening the main switch,thereby breaking the work circuit.

It will of course be understood that as the armature 5I52 falls,carrying the leaf spring IIII with it, the leaf spring 82, acting on therocker 95, returns the latter to the Fig; l position, and at the sametime permits the pilot switch 63 to open, so that the electromagnetthereafter remains deenergized until the control button I3 has againbeen depressed, even though the overload switch 64 in the meantime mayhave automatically reclosed, as a result of the breaking of the motorcircuit and the consequent cooling and reflex action of thatthermostatic strip I26 which had caused the switch 64 to open.

It will thus be noted that whenever the circuit is broken by the openingof one of the overload switches 66, the main switch opens, and also thepilot switch 63 opens as a result of the opening of the main switch. Infact the main switch "opens whenever any break occurs in the circuit orwhenever the voltage therein falls below that required to hold the mainswitch closed, and whenever the main switch opens, the pilot switchalways opens automatically in the manner above described, so that in theevent of failure inthe main circuit from whatever cause the pilot switchopens automatically. This is important from a practical standpointbecause it requires a deliberate act of the operator to re-close thepilotv main switch, and yet possessing all of the desirable functionalcharacteristics of the much more complicated and cumbersome motor con.-

trolling devices now in common use. It will also be noted that all ofthe parts may be readily formed and easily assembled at minimum cost,the same being so combined in sub-assembly arrangements as to be readilyremovable for purposes of inspection, replacement, and repair.

The motor controller described may also readily be placed under remoteswitch control without modification of the structural parts thereof.Fig. 8 illustrates how the circuits may be modified to provide forremote control. As therein shown, the shunt circuit 62, containing thecoil 46 of the electromagnet, the pilot switch 63, and overload switch64 is extended to a remote control panel I3I having two auxiliarycontrol switches I32 and I33. Switch I32 is a normally closed switchconnected in the circuit 62. Switch I 33 is a normally open switchdisposed in an auxiliary circuit bridged across the pilot switch 63.

The arrangement is such that when the pilot switch 63 is open, asindicated in Fig. 8, the circuit 62 may be closed by momentarily closingthe normally open switch I33, so as to energize the coil 46 of theelectromagnet and thereby effect actuation of its armature 5I-52 and theswitch bar 40 into the Fig. 2 position to close the main switch. Thismovement of the armature is transmitted through the spring IOI to therocker element 95 in such manner'as to close the pilot switch 63, sothat on subsequent reopening of the switch i33 the circuit 62 remainsclosed through the switch 63. When it is desired to reopen the mainswitch, this may be accomplished by momentarily opening the switch I32,thereby breaking the circuit 62 and de-energizing the coil 46 of theelectromagnet. When this occurs, the armature 5I-52 falls, retractingthe switch bar 40 and opening the main switch, the pilot switch 63 alsobeing reopened'by the spring 84fas the spring IIII lowers with thearmature.

The motor controller illustrated in Figs. 9 to 13 is similar in manyrespects to that shown in Figs. 1 to 6, but is simpler nd more compact.All of the parts are carried by a mounting plate I4 removably fixedwithin an appropriate housing I having a removable cover II having acupped opening I2 to accommodate the single control button I3.

The pairs of fixed contacts II and I8 of the main switch are arranged ina supporting structure 20' of insulating. material strikingly similar tothat shown in Figs. 1 and 2, and the movable contacts 33 and 34 arecarried by a movable switch actuating bar 40' in a strikingly similarmanner. In this. instance, however, the switch bar 4|! is supported andguided by two pairs of bars 58 which are in turn supported upon andguided by the frame of the electromagnet in a manner to be laterdescribed.

The electromagnet shown comprises a coil or winding 46 supported uponthe core 41' of a laminated E-shapedfield piece in which theiaminatiQnsare, rigidly bound together between .fianged frame plates48', one of which is removably fixed to an appropriate supportingbracket 50 fixed to the mounting plate I4. The armature of theelectromagnet comprises a similar laminated E-shaped structure in whichthe laminations are bound together between flanged frame plates ,52',the armature being supported and guided largely by the pairs of bars 58'abov mentioned.

The bars 58 of one pair ride freely upon the exposed face of one of thestationary frame plates 48, the flange 45 at one edge of the plate 48being cut away, as at H, to receive and guide" the bars, the bars beingfurther guided by the upturned side flanges 43 extending parallelthereto. The other pair of bars 58' are similarly arranged with respectto the opposite frame plate 48. Both pairs of bars 58' are securely butreleasably fixed at their upper ends to the switch lower ends 4| beingturned outwardly and se-' curely clamped against a flange of ,60 on aframe plate 52 of the armature by the overlying ends SI of a clamp bar62, releasably clamped to the flange 60' by an appropriate screw 64'.The switch bar 40' and the armature 5| are thus rigidly united by thebars 58 for straight line movement, as a unit, in a direction lengthwiseof the bars and axially of the electromagnet.

The coil 46 of the electromagnet is controlled by a normally open pilotswitch 63' similar in many respects to the pilot switch 63 hereinabovedescribed, it being enclosed in a housing 61 of insulating materialfixed to and supported by a bracket plate 85' which in turn is mountedbetween and releasably interlocked with two upstanding bracket plates51' in a manner similar to the above described relation between thebracket plate 85 and support 51.

The pilot switch shown at 63' includes two stationary contacts 69,having separate terminals I0, and connectable by a bridge member I2carrying movable contacts 'II. As in the switch 63, hereinabovedescribed, the bridge member I2 is carried by one end of a rocker plateI3 fulcrumed at its other end I4, a tension spring 17' connecting themovable end of the plate I3 with the movable end I8 of a rocker controlplate 79' fulcrumed at its other end 80. The arrangement is such thatthe spring 11' always urges the control plate I9 to swing toward theright from the position shown in Fig. 9.

It will be understood of course that in the Fig. 9 position of thecontrol plate IS the position of the spring TI is such as to yieldablyhold the switch carrier plate I3 in the position shown, so that theswitch is closed, but that when the control plate I9 is swung toward theright from that osition, the spring shifts to the opposite side of thefulcrum point I4 of the switch carrier plate I3, causing the switch toopen with a snap action, and to remain open until the control plate I9is again swung toward the Fig. 9 position, causing the switch to closewith a snap action.

In this instance the control plate I9 is controlled by a lever 84rockably supported on a fixed pivot pin 92' and controlled by a rockerelement 35 similar to the element 95 hereinabove described. In thisinstance one end of the lever 84 bears against the end I8 of the controlplate I9 and the other end bears against a shoulder 93 of the rockerelement The rocker element 95 is also provided with a shoulder 99' forcoaction with a vertical push plate I00 slidably mounted and guided byand between pairs of hook-like lugs 86 formed on the rear side of thebracket plate 85; The push plate Hill is yieldably supported at itslower end by one end of a leaf spring III'I', which is attached at itsother end to the armature SI for movement therewith.

The arrangement is such that when the armature 5| moves upwardly intothe Fig. 9 position to close the main switch, the spring'IlI urges 7 thepush plate III! to move upwardly with it into such position as toyieldably retain the rocker element 95 in the position shown, in

spring IN and plate It!!! lowers with it, there by releasing the rockerelement 95 and permitting it and the lever 84' to rock in such directionas to permit the control plate I9 to swing towardthe right (Fig. 9) andthus induce the pilot switch 63 to open.

Like the rocker element 95, hereinabove described, the rocker element 95is provided with stop shoulders 91' and 98' which coact with a plate 88to limit the range of rocking movement thereof, and is also providedwith V-shaped recesses III) and III on opposite sides of the pivotalsupport, 96' thereof which coact alternatively with a pointed dog I05 toefiect rocking action of the rocker element from either extreme positionto the other whenever the push button I3 is depressed.

The arrangement is such that with the several parts in the positionsshown in Fig. 9, a depression of the push button I3 will cause the dogI05 to enter the recess II I and force the rocker element 95 clockwise,forcing the push plate I downwardly against the resistance of spring NH,and permitting the control plate I? to swing toward the right andthereby open the pilot switch 63. Opening of the pilot switch 63" ofcourse de-energizes the coil 65 of the electromagnet, causing thearmature III to drop and open the. main switch. *The main switch remainsopen until the push button I3 is again depressed, whereupon the dog I05,entering the recess IIll, forces the rocker element 95'counter-clockwise, returning it to the position shown in Fig. 9 andthereby closing the pilot switch 63'. Closing of the pilot switch ofcourse energizes thecoillfi; causing the armature 5i to rise and therebyclose the main switch.

Provision is made for automatically opening the main switch in the eventof overload in the work circuit. As in the device hereinabove described,this isaccomplished by the heater coils 65 in difierent sides of thework circuit together with temperature responsive elements I26associated therewith. thethermostatic elements I26 are made to act uponthe pilot switch 63, thereby obviating the;

necessity of a second auxiliary switch, such as the switch 64 employedin the device above described.

In this instance each heater coil is in the form of a metallic strip 65'detachably supported at its ends by C-shaped brackets I28, and I29mounted within a channel-like structure I30 of insulating materialbolted or otherwise attached to one or the other of the bracket plates51'. A removable cover I35 is provided for each structure I30. Abi-metallic thermostatic strip I26 is anchored at one end in bracket I28and extends close to the heater strip 6.5 and loosely into the bracketI29. A push bar I36 of insulating material rests at one end against thefree end I25 of each thermostatic strip and extends through the coverI35 into engagement with one end of a lever' I38 fulcrumed on a bracketI39 attached to a side of the pilot switch housing 61. Theother end I40of each lever I38 projects into the housing 61' and overlies theswitchcarrying rocker plate I9. The leverends I40 are normally yieldablysustained clear OffthG rocker plate Is by a suitable. spring Ill.

bar I35 in such direction as to rock one of the levers I38 and therebyforce the rocker plate I3 and switch contacts II away from the contacts69' so as to open the pilot switch 53. It will be understood of coursethat as the temperature of the strip I26 rises it exerts an increasingupward pressure against the push bar I36 untilthat pressure is sumcientto overcome the resistance to opening movement of the switch element73', so that when the switch 53' does open, it opens with a snap action,7 I

It will also be understood that, when the pilot switch 63 is opened inthis manner, the coil 36' of the electro-magnet becomes de-energized andthe armature 5I' lowers to open the main switch and to permit the rockerelement 95, lever I06, and control plate I9, to shift into the positionsnormally assumed by them when the pilot switch is open. r

A special reset mechanism is preferably provided to prevent re-closingof the pilot switch 63 and consequently/bf the main switch, until thereset mechanism has been manipulated. For this purpose a spring detentM2 is provided adjacent the outer end I 53 of each lever I38 anddesigned to retain the same against return movement after it has beenactuated by the thermostatic strip I26 and bar I36 into switchopeningposition. As illustrated particularly in Fig. 11,

each detent H32 comprises a spring strip having a tooth formationItfladapted to enter beneath and support the end N3 of the adjacentlever to support the latter against downward movement after it has beenelevated by its coacting push at) bar E36.

In this instance, however,

'mally functions to hold the actuated lever 138' Both detents 52 may beforced entirely clear of their associated lever ends M3, so as torelease the latter, by a reset bar M5 having camlike end portions M5arranged to coact with and spread apart the inclined end portions Ml ofthe detents when the bar M5 is depressed (Fig. 11). In this instance thebar M5 is yieldably supported against the interior cover II by a springwe mounted on the cover, the bar having a fiat projection I49 extendingthrough and guided by an appropriate opening in the cover, theprojection I69 constituting a convenient means for depressing the barI35 into wedging contact with the detents Hi2.

It will thus be noted that after the pilot switch 63 has been opened byactuation of either of the levers I38, the cooperating detent I42 norinsuch position as to hold the switch 53 open, thereby making itimpossible to close the switch 63' until after the reset bar M5 has beendepressed in the manner described. In some instances it may be desirableto permit reclosing of the switch 63 after it has been automaticallyopened by one of the,levers I38 in response to the thermal unit, withoutrequiring separate manipulation of the reset bar I45. This may beaccomplished by fixing the bar'I45 in depressed position by passinga pinthrough a hole I50 in the bar afterthe hole has been'lowered beneath theinterior surface of the cover II'. In that depressed position of the barM5, the ends us I of thedetents I42 are spread apart so as to render thelatter inefiective upon the levers-l38.

Various changes may be made in either embodiment of the inventionhereinabove specifically described without departing from orsacrificingthe advantages of the invention as defined in the appendedclaims.

I claim:

1. In' a circuit controller the combination of a main switch forcontrolling a circuit, electromagnetic means energized from the circuitfor operating said main switch, a pilot switch operable to effectenergization and de-energization of said electromagnetic means, anelement altere natively operable to close or open said pilot switch, andmeans for resisting opening of said pilot switch while saidelectromagnet is energized, whereby said pilot switch functions as astart switch, a holding switch, and a stop switch.

2. In a circuit controller the combination of a main switch forcontrolling a circuit, electromagnetic means energized from the circuitfor closing said main switch, a pilot switch operable to effectenergization and de-energization of said electromagnetic means, anelement alternatively operable to close or open said pilot switch, andmeans responsive to opening ofsaid main switch for opening said pilotswitch.

3. In a circuit controller the combination of a main switch forcontrolling a circuit, electromagnetic means energized from said circuitfor operating said main switch, a pilot switch operable to effectenergization and de-energization of said electromagnetic means, saidpilot switch being biased toward open position, a control elementalternatively operable to close or open said pilot switch, andadditional means normally effective to hold said pilot switch closedwhile said main switch is closed and for effecting opening ofsaid pilotswitch in response to opening of said main switch.

4. In a circuit controller the combination of a mainswitch forcontrolling a circuit, an electromagnetic actuator for said switch,electrical connections through which said electromagnetic actuator isenergizable from the circuit, a control element alternatively operableto close and open said connections, and additional means operable toopen said connections in response to opening of said main switch.

5. In a' circuit controller the combination of a main switch forcontrolling a circuit, an electromagnetic actuator fOr saidswitch,electrical connections through which said electromagnetic actuator isenergizable from the circuit, a control element having a singleactuating movement, means responsive to actuation of said element forclosing and. opening said connections alternatively, and means operableto open said connections in response to opening of said main switch.

6. In a circuit controller the combination of a main switch, anelectromagnetic actuator therefor, an element having an actuatingmovement and an idle movement, and means responsive to actuatingmovements of said element for alternatively energizing and de-energizingsaid actuating movements of said element for alternatively energizingand de-energizing said actuator, said means including switch meansoperable in response to switch openingmoveinent of said actuator, andmeans effective to de-energize said actuator independently of saidelement.

8. In a circuit controller the combination of a main switch, anelectromagnetic actuator therefor, switch means for controllingenergization of said actuator and automatically operable in response toswitch-opening movement of the latter, said switch means including asingle control element operable to effect energization anddeenergizationof said actuator alternatively, and means operable toeffect de-energization of said actuator independently of said element.

9. In a circuit controller the combination of-a main switch forcontrolling a circuit, an electromagnetic actuator for said switch,switch means for controlling said actuator and operable in re.

sponse to switch-opening movement of the latter, said switch meansincluding a single control element alternatively operable to effectenergization and de-energization of. said actuator, and means ,and meansresponsive to an overload condition on any of a plurality of sides ofthe circuit for de-energizing said actuator.

11. In a controller for a multi-sided circuit the combination oi amultiple switch alternatively operable to close the sides of the circuitand to open the sides thereof, an electromagnetic actuator for saidmultiple switch, electrical connections through which said actuator isenergizable from the circuit, an element alternatively operable to closeand open said connections to thereby effect energization andde-energization of said actuator, means responsive to switch-openingmovement of said actuator for opening said connections, and meansresponsive to an overload condition in any of a plurality of sides ofthe circuit for Opening said connections to thereby de-energize saidactuator.

12. In a controller for a multi-sided circuit the combination of amultiple switch alternatively operable to close the sides of the circuitand to open the sides thereof, an electromagnetic actuator for saidmultiple switch, a pilot switch i'or controlling said actuator, anelement movable to close andopen said pilot switch alternatively, andmeans responsive to an overload condition on any of a plurality of sidesof the circuit for opening said pilot switch and thereby to .de-energizesaid actuator. V

13. In a controller for a multi-sided circuit the combination of amultiple switch alternatively operable to close the sides of the circuitand to open thesides thereof, an electromagnetic actuator for saidmultiple switch, electrical connections through which said actuator isenergizable, a switch in said connections normally eiIective to controlsaid actuator, a normally closed switch in said connections, and meansresponsive to an overload condition in any of a plurality of sides ofthe circuit for opening said last named switch and thereby tode-energize said actuator.

'14. In a circuit controller the combination of a main switch forcontrolling a circuit, an electromagnetic actuator for said switch,electrical coning said pilot switch in response to switch-openingmovement of said actuator. 15. In a circuit controller the combinationof a main switch for controlling a circuit, an electromagnetic actuatorfor said switch, electrical connections through which said actuator isenergizable from the circuit, a pilot switch in said connections forcontrolling said actuator and operable in response to switch-openingmovement of the latter, means responsive to a load on said circuit foropening said connections, and means operable independently of said lastnamed means for closin and opening said pilot switch.

16. In a circuit controller the combination of a main switch forcontrolling a circuit, an electromagnetic actuator for said switch,electrical connections through which said actuator is energizable fromthe circuit, means responsive to a load on the circuit for opening saidconnections, a pilot switch in said connections operable in response toswitch-opening movement of said actuator, means operable independentlyof said last named means for opening and closing said pilot main switch,an electromagnetic actuator there- .for, a moveable control element,means alternatively efiective to energize said actuator in response tomovement of said element in one direction and to de-energize saidactuator in response to movement of said element in the same direction,and additional remote control means for said actuator.

20. In a circuit controller the combination of a main switch, anelectromagnetic actuator therefor, a moveable-control element, switchmeans alternatively efiective to energize said actuator in response tomovement of said element in one 1 direction and to de-energize saidactuator in remain switch, an electromagnetic actuator thereswitch, andmanually releasable means normally efiective to prevent closing of saidconnections after the latter have been opened by said load responsivemeans.

17. In a circuit'controller the combination of a main switch forcontrolling a circuit, an elecand means for rendering said last namedmeans ineffective. r

18. In a circuit-controller the combination of a main switch, an.electromagnetic actuator therefor, and means for controlling saidactuator, said means including a control element moveable to effectenergization orde-energization of said actuator, and remote controlmeans operable independently of said element to efiect energization orde-er lergizationof said actuator.

19. In a circuit controller the combination of a for, a depressablecontrol element, switch means alternatively effective to energize saidactuator upon depression of said element and to tie-energize saidactuator upon depression of said element, and means responsive to a dropin voltage for opening said switch means.

22. In a circuit controller the combination of a main switch forcontrolling a circuit, electromagnetic means energized from the circuitfor operating said main switch, a pilot switch operable to eiiectenergization and de-energization of said electromagnetic means tothereby effect; opening and closing of said main switch, means foropening and closing said pilot switch, and means responsive to saidelectromagnetic means for holding said pilot switch closed when saidmain switch is closed, said last named means being yieldable to permitopening of said pilot switch when said main switch is closed to therebyefiect opening of said main switch.

23. In a circuit controller the combination of a main switch forcontrolling a circuit, electromagnetic means energized from said circuitfor operating said main switch, a pilot switch operable to effectenergization and deenergization of said-electromagnetic means, means forclosing and opening said pilot switch to thereby efiect closing andopening of said main switch, additional means for effecting opening ofsaid main switch, and means for insuring opening of said pilot switchwhenever said main switch is opened.

24. In a circuit controller-the combination of a main switch forcontrolling a circuit, electromagnetic means energized from the circuitfor closing said main switch, a single pilot'switch alternativelyoperable to efiect energization or deenergizatiom of saidelectromagnetic means, and means responsiveto a drop in voltage in saidcircult for opening said pilot switch.

LYLE 'BEEMAN.

